A circuit includes a battery with electromotive force $E$ and internal resistance $r$, linked to two resistors, each having resistance $2.5\,\Omega$. The resistors are arranged in parallel, as shown. The current through one of the resistors is $0.80\,\text{A}$. Which expression, with $E$ measured in volts and $r$ measured in ohms, determines the internal resistance $r$?
- A$\frac{E - 4.0}{1.6}$
- B$\frac{E - 4.0}{0.80}$
- C$\frac{E - 2.0}{1.6}$
- D$\frac{E - 2.0}{0.80}$